'91 D250 Cruise Control Trouble Shooting

[Warhorse]

I got this truck in December and I have just about finished all of the mechanical stuff that was wrong with it. The last thing on the list is the cruise control. Fuse is good. I have checked the module on the driver-side fender--it has a good vacuum source, and holds vacuum when a vacuum pump is applied. When I click the switch on the steering wheel, there is power to the plug on the module. I removed and cleaned the VSS (strange thing--there was a staple inside the connector shorting across the two pegs) and put it back on; speedometer is steady with no fluctuations so I think the VSS is ok. I guess the next steps are:
1. check the set/decel switch and the accel switch on the steering wheel, but I'm not sure how to do that.
2. check adjustment of the brake light switch--not sure how to do that either.
Are there any other components to the cruise control?
Any and all help would sure be appreciated! Thanks!

 

[AnonEd]

The FSM flow chart for no cruise when set/decel in order: Fuse blown > no vacuum @ servo > cruise cable disconnected > improper brake light/speed control switch adjustment > faulty elect circuit.

Switch continuity chart (switch fasteners under horn pad, which I think unscrews from behind):
OFF pin 1 and 4
ON pin 1 and 4, pin 1 and 2, pin 2 and 4
ON and SET pin 1 and 2
ON and RESUME pin 1 and 3

Brake light/speed control switch test:
Dicsonnect connector. With brake pedal released no resistance between
*BLACK and WHITE/RED
*YELLOW/RED
*DARK BLUE/RED
*the PINK and WHITE wires

With brake pedal depressed, should be continuity between PINK and WHITE, no continuity between
*BLACK and WHITE/ED
*YELLOW/RED
*DARK BLUE/RED

Switch adjustment:
1. Push switch through clip in mounting bracket until switch is sealed against bracket. Brake pedal will move forward slightly.
2. Gently pull back on brake pedal as far as it will go.
3. Switch will ratchet rearward to correct position. Further adjustment is not required.

Good luck. Note that if the truck was tuned up the cruise may not work very well...since mine fuels more it tends to lunge adding fuel, since more cable movement adds more fuel than stock calibration. It is handy at full speed, but a brick would work just as well.

 

[Warhorse]

Thanks! I'll go through these steps and hopefully I can get it working.